Study On Failure Mechanism Of Rock Slope And Deformation Monitoring Under Freezing-thawing Cycles

Our country is one of the world's largest distribution in cold regions,which accounts for about 75% of the total land area,and fractured rock mass in these areas is a ubiquitous class of complex media,due to repeated freezing-thawing damage caused by the deterioration of its strength,increasing deformation,will directly affect the design and construction of rock engineering,and put into use after operations.With the development of large-scale construction in alpine mountains,more and more fractured rock freezing problems caused concern among the people.Based on the strong frost weathering under the environment of the Pakistan highway and the tianshan highway as an example,proposed in the full understanding of the development of two highways along the collapse distribution,on the basis of the combination of 3D laser scanning field survey and data processing of collapse,and carry out the cycle of fractured rock mass frost heave test and ice split test,exploring the alpine region rupture mechanism of rock mass under the condition of cyclic freezing-thawing.At the same time,in order to later in the alpine region in the process of the construction and operation maintenance of highway construction to achieve the timely and effective monitoring,the collapse in the study area typical collapse deformation monitoring and analysis of the deformation trend,through the above study of the following main results:(1)Collapse were investigated in the Pakistan highway and the tianshan highway,in order to find out the general situation of the collapse of a tow line in distribution and get alpine region on the basis of summarizing development distribution of the collapse: the effect of landform,lithology effect,slope body structure effect,the effect of geological structure and climate effect.(2)The freezing-thawing strain tests on the dry and saturated fractured rock mass were carried out under the change temperature.It was found that the strain processes were very different under the two states in a freezing-thawing cycles.Dry fractured rock mass occurs linear elastic deformation,while saturated fractured rock mass experiences eight stages: shrink stage,frost heave stage,frozen shrink stage,temperature hysteresis stage,thermal expansion stage,melting contraction stage,melting retracted shells stage,melting contraction stabilization stage.Within a freezing-thawing cycle,dry fractured rock mass is basically not produce residual deformation,while saturated fractured rock mass significant residual deformation.whatever fractured rock mass,its biggest micro-strain values increased with increasing number of cycles under different freezing-thawing cycles.(3)The freezing-thawing strain tests on saturated fractured rock mass were carried out under the constant temperature.The test results show that the largest micro-strain of fractured rock constant with decreasing temperature increases,the magnitude and speed of the different lithologies fractured rock mass' s largest micro-strain increases were different.At the same time,defining expansion and contraction rate ? to reflect the effects of expansion and contraction of saturated fractured rock mass under the effect of freezing-thawing.(4)The circular freezing-thawing ice splitting tests on fractured rock mass were carried out.Analyzing the regularity of crack growth and extension of different lithology of fractured rock mass under circular ice splitting,and summarizing five models of freezing-thawing deterioration for fractured rock mass: layered shedding mode,block off mode,chip mode,crack model and along the artificial slit fracture mode.At the same time,summed up the characteristics of the evolution of the crack and investigating the fracture mechanism of fractured rock mass under freezing-thawing cycles.(5)According to the typical collapse in high and cold area,design the deformation monitoring and early warning,put forward the analysis method of deformation monitoring and early warning index,determine the index threshold and collapse deformation level;At the same time,through 3D laser scanning technology for deformation monitoring of typical collapse in high and cold area,using multiphase scanning data contrast analysis,gets its deformation law,analyzes the trend of deformation.